Nephelometry of apolipoprotein B in human serum.

We studied the development of light scattering in the reaction between anti-apolipoprotein B and apolipoprotein B in intact very-low-density lipoproteins (I) and low-density lipoproteins (II) as well as in lipoproteins treated with lipases, and found considerable differences in the kinetics of the immunoreaction for the two lipoprotein classes. Pre-incubation with triglyceride lipase and cholesterol esterase caused a decrease of final light scattering in I but only minimal changes in the reaction with II. Non-ionic detergent not only decreased the original light scattering in hyperlipemic serum samples, but also accelerated the immunoreaction. Under standardized conditions, results of quantitative nephelometry correlated highly significantly with quantitative determination of apolipoprotein B by radial immunodiffusion, both for normolipemic and hyperlipoproteinemic serum samples. The nonspecific light scattering caused by neutral lipids in intact lipoproteins could be minimized when samples were pre-incubated with lipolytic enzymes.